Field of the invention
The present invention relates to a control method for a vehicle with a DCT and, more particularly, to a method of controlling a vehicle with a DCT when a wheel speed sensor fails.
Description of Related Art
A Dual Clutch Transmission (DCT) is configured to appropriately adjust and output power from two input shaft to one output shaft through two clutches and there is a DCT which is provided with only two input shaft speed sensors for measuring the speeds of two input shaft without an output shaft speed sensor.
In a vehicle provided with a DCT without an output shaft speed sensor, a signal is received from a wheel speed sensor on a wheel of the vehicle during shifting and the output shaft speed of the DCT is determined on the basis of the signal to be used for shifting.
The signal from a wheel speed sensor is transmitted through a communication system such as a Controller Area Network (CAN), so when the wheel speed sensor fails or the CAN fails, a Transmission Control Unit (TCU) controlling the DCT has to appropriately cope with the failure.
As described above, a TCU controlling a DCT cannot normally receive a signal from a wheel speed sensor due to failure of the wheel speed sensor or a CAN (which is called a “wheel speed-unknown state” hereafter). In the instant case, if a vehicle is driven at a high speed and IG-OFF and IG-ON sequentially occur due to the intention of a driver, the TCU controlling the DCT cannot recognize that it was the wheel speed-unknown state before IG-OFF immediately after IG-ON, so that the TCU pre-engages the DCT on the basis of the DCT output shaft speed determined on the basis of a wrong signal from the wheel speed sensor immediately after IG-ON, so lower-gear pre-engagement may occur.
When a very low-shifting gear is pre-engaged while a vehicle is driven at a high speed, for example, when a low-shifting gear such as the first gear or the second gear is pre-engaged while a vehicle is driven at a high speed with the fifth gear engaged in comparison to the vehicle speed, the clutch of a non-driven input shaft associated with the gear to be pre-engaged is rotated at a high speed over about 9000 RPM, so that the clutch may break, which is called clutch burst.
For reference, IG-OFF and IG-ON mean turning off and on an engine in a vehicle provided with an engine, and in an electric vehicle or a hybrid vehicle without an engine, they mean operations corresponding to turning off and on an engine in a vehicle provided only with an engine by a driver.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.